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New Furnace/AC Time

We live in Northern NJ (Berkeley Heights) & have a 1,850 sq ft Split Level, built in 1955.

Our current furnace is a forced hot air Bryant Model 397G, installed in 1979/1980, and Bryant 3 Ton Central A/C added in 1985. Both seemed to be sized correctly for the house, as we have not had any problems with either the furnace or A/C running excessively & good humidity control in the house.

The furnace ID Plate states 125,000 Input BTU/hr, Bonnet Capacity of 100,000 BTU/hr. The current Central A/C has a SEER of 10.3.

We have had no major problems in the past with these units, but last week it appears as though a water leak has developed in the collection pan for the evaporator coil. The condensate water is leaking all over the cellar floor instead of going out the furnished drain fitting.

Before this problem came up, we were toying with the idea of replacing these units for higher efficiency units, but had pretty much decided to put it off for a year or two. This problem with the condensate water changed our minds pretty quickly & now we want to take care of replacing these units this year.

We have had two contractors come by & furnish estimates, both using York equipment, one a 100,000 BTU furnace, 3 Ton A/C Unit & Coil. The other estimate has a 115,000 BTU furnace, 3 Ton A/C Unit & Coil. There is another contractor that will show up shortly.

One of the contractors said that we could not make a direct comparison of the BTU Rating of our current Furnace with the units currently on the market because the method of measuring BTU's of these units has changed. Is this the case?

Also, what does "Bonnet Capacity" mean on our current furnace's I.D. Plate, as opposed to "Input" for the BTU's?

One of the contractors said that we could not make a direct comparison of the BTU Rating of our current Furnace with the units currently on the market because the method of measuring BTU's of these units has changed. Is this the case?

Kind of irrelevant. Your contractor needs to do a "Manual J" heat gain/loss and size the system properly for how your house is now in 2008, not 1955.

Unfortunately, most contractors use the by-gosh-and-by-golly rule-of-thumb method for sizing equipment, which may work OK enough, if you don't mind short equipment lifetimes and high energy bills.

York Latitude or Affinity Series & Reliability

So, we've had three contractors come by & all three have proposed York equipment.

Two of them have proposed York Latitude Series, the third proposed the higher efficiency York Affinity Series.

Even though the Affinity Series has higher efficiency, one of the contractors that proposed the Latitude Series suggested that the higher efficiency furnaces such as the Affinity Series have reliability problems, especially with circuit boards.

I'd like to know what the experience of the folks on this site have had as far as reliability is concerned with the York Affinity Series compared to the Latitude Series.

The BTU input to output is still done the same. He may have been refering to AFUE being the rating system today. Which is its performance for the year. Where your currnet furnace only has a Steady State Efficiency rating.

If a load calc was done. Good chance you'd find that a 80,000 BTU 95% will heat your house.
Newer furnaces need to move more air then the older ones did. So sizing is important.
If a contractor tells you that the furnace size isn't too important if they use a 2 stage furnace. They're BS ing you.

Let's talk about a few things -

I live in NJ too. The first floor of my 1948 house is 1550 square feet. I have a 45,000 BTU gas furnace happily heating it. Houses are all different - you need accurate heat load calculations done to determine what You need. I am not telling you what you need, but I'm thinking that the smart money would be betting Against a 100,000+ BTU furnace requirement. <g>

Next - if you are buying an air conditining system anyway - do yourself a huge favor and pay the few percentage points more and get a nice heat pump system installed along with your new furnace - instead of just the straight AC. Running the HP during at least half our winters will save you about 30-40% on your heating cost during that time. If your contractors wrinkle their nose or frown before telling you not to buy a heat pump - they are not on your side in this fight. I can back that up with some real numbers if you think I might be a crack-pot. <g>

Bonnet Capacity = Input

Furnaces used to be rated based on stack loss = so much gas burned = so many BTU's. Subtract what went up the stack from that and the remainder was assumed to be provided to the consumer.

Now furnaces are rated based on heat output to the conditioned space and the remainder is assumed to be stack and other losses. Which is a much fairer description of what the consumer will actually receive.

Do yourself two favors - get several accurate heat load calculations done on your house as it exists today. From isolated sources. If they don't agree - find out why. Have them do both heating and cooling. And buy a heat pump to go along with your furnace. You checkbook will thank you for decades to come.

PHM
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Originally Posted by mbushnell

We live in Northern NJ (Berkeley Heights) & have a 1,850 sq ft Split Level, built in 1955.

Our current furnace is a forced hot air Bryant Model 397G, installed in 1979/1980, and Bryant 3 Ton Central A/C added in 1985. Both seemed to be sized correctly for the house, as we have not had any problems with either the furnace or A/C running excessively & good humidity control in the house.

The furnace ID Plate states 125,000 Input BTU/hr, Bonnet Capacity of 100,000 BTU/hr. The current Central A/C has a SEER of 10.3.

We have had no major problems in the past with these units, but last week it appears as though a water leak has developed in the collection pan for the evaporator coil. The condensate water is leaking all over the cellar floor instead of going out the furnished drain fitting.

Before this problem came up, we were toying with the idea of replacing these units for higher efficiency units, but had pretty much decided to put it off for a year or two. This problem with the condensate water changed our minds pretty quickly & now we want to take care of replacing these units this year.

We have had two contractors come by & furnish estimates, both using York equipment, one a 100,000 BTU furnace, 3 Ton A/C Unit & Coil. The other estimate has a 115,000 BTU furnace, 3 Ton A/C Unit & Coil. There is another contractor that will show up shortly.

One of the contractors said that we could not make a direct comparison of the BTU Rating of our current Furnace with the units currently on the market because the method of measuring BTU's of these units has changed. Is this the case?

Also, what does "Bonnet Capacity" mean on our current furnace's I.D. Plate, as opposed to "Input" for the BTU's?

PHM
--------
The conventional view serves to protect us from the painful job of thinking.

With a 50+ year old house, adding insulating and draft proofing should be your top priority.

We went through a lot of that when we installed the present furnace in 1978. At that time, we switched from an oil fired to a gas fired furnace & we were required to make improvements in order to make the switch.

We added insulation in the attics, storm windows all around (most have been replaced with thermal pane glass by now), etc. I was away at college at the time, so I don't know all of the details, but I remember my dad saying all of the things that he had to do.

We even have a home-made hinged insulated panel over the attic pull-down stairway.